Fluid displacement units

ABSTRACT

A displacement unit for delivering quantities of fluid, particularly lubricant, in response to changes in the pressure of fluid supplied to it, comprises a housing chamber having an inlet and an outlet, first and second pistons movable in said chamber, and resilient means biasing the first piston, and with it the second piston, towards said inlet, the first piston having a passage through it which is closed during a delivery stroke by the second piston and a restricted passage being provided past said second piston, such that the supply of fluid under pressure to the inlet moves both pistons together towards the outlet to discharge fluid from the chamber, fluid then entering a space behind the first piston through said restricted passage, whereas a drop in the inlet pressure causes fluid pressure in the said space to move the second piston away from the first to allow the discharge through said passage of fluid from said space.

United States Patent [72[ Inventor Max Edward Grantham Plympton,Plymouth, Devon, England [21 Appl. No. 768,640 [22] Filed Oct. 18, 1968[45] Patented June 1, 1971 [73] Assignee Tecalemit Engineering LimitedPlymouth, Devon, England [54] FLUID DISPLACEMENT UNITS 13 Claims, 2Drawing Figs.

[52] 11.8. C1 417/377 [51] Int. Cl F04b 17/00 [50] Field of Search103/44 [56] References Cited UNITED STATES PATENTS 2,555,613 6/1951Soberg 103/44 2,877,712 3/1959 Mc Gay l03/44X 3,333,425 8/1967 Hemard230/52X Primary ExaminerRobert M. Walker A!lorneyMason, Mason & AlbrightABSTRACT: A displacement unit for delivering quantities of fluid,particularly lubricant, in response to changes in the pressure of fluidsupplied to it, comprises a housing chamber having an inletand anoutlet, first and second pistons movable in said chamber, and resilientmeans biasing the first piston, and with it the second piston, towardssaid inlet, the first piston having a passage through it which is closedduring a delivery stroke by the second piston and a restricted passagebeing provided past said second piston, such that the supply of fluidunder pressure to the inlet moves both pistons together towards theoutlet to discharge fluid from the chamber, fluid then entering a spacebehind the first piston through said restricted passage, whereas a dropin the inlet pressure causes fluid pressure in the said space to movethe second piston away from the first to allow the discharge throughsaid passage of fluid from said space.

FLUID DISPLACEMENT UNITS SUMMARY OF THE INVENTION This invention relatesto units which are operated by pressure changes or signals in a fluidwhich is supplied to the unit, in order to give an output which consistsof a number of deliveries of predetermined quantities of the fluid.

It is an object of the invention to provide novel and improved units forthis purpose which are economical in construction and efficient in theiroperation.

The invention provides a fluid displacement unit for deliveringpredetermined quantities of a fluid supplied to it under pressure inresponse to periodic increases and decreases in the said pressure, saidunit comprising:

a housing chamber having an inlet and an outlet for said fluid,

a first piston which is reciprocable in said chamber and has a fluidpassage extending through it,

a second piston which is movable in said chamber between said inlet andsaid first piston which it engages to close said passage, said pistonstogether dividing a reserve space in part of said chamber from saidinlet and said outlet except for a constricted passage for allowingfluid under pressure to flow from said inlet and said space past saidsecond piston, and

resilient means biasing said first piston against said second pistonto'close said passage whereby a supply of fluid to said inlet underpressure acts on and moves both said pistons together away from saidinlet and against the force of said resilient means to discharge fluidfrom said chamber to said outlet while fluid from said inlet enters saidreserve space through said constricted passage, whereas a drop inpressure in said inlet allows said resilient means to return said firstpiston to its original position, the pressure of the fluid in saidreserve space first moving said second piston away from said firstpiston to allow this fluid from said space to be discharged through saidpassage.

In a preferred embodiment of the invention the second piston member is aball which acts as a valve to close either or both the fluid inlet andthe passage through the first piston member, while constricted passagemay be formed by a clearance between the ball and the wall of thehousing chamber.

The biasing member is preferably an annulus of resilient material whichmay also seal the communication between the said space and the outletport, when the passage through the first piston member is closed by theball.

Alternatively, the biasing means may be a helical spring and the saidspace may be is sealed from the outlet by the first piston member makingfluidtight sliding contact with the housing.

The clearance between the second piston member or ball and the wall ofthe chamber will be selected to prevent cavitation behind the firstpiston member on the pumping or delivery stroke while keeping downleakage past this member during the initial stages of the return stroke.

The unit' which has been described combines a small size and simplicityof operation with the ability to react, without BRIEF DESCRIPTION OF THEDRAWINGS FIG. 1 is a longitudinal section of one embodiment and F IG, 2is a longitudinal section of another embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, thegenerally cylindrical body part 1 has an axial central inlet duct 9extending from one end of the part to the other and widening by steppedincrements towards the other end to form a housing chamber in which themoving parts of the unit are positioned. This chamber is not specifically indicated in the drawing, for the sake of clarity, and it isdelimited by one end wall 18 of a second body part 2 which makes a fitwith the other end of the body part 1. The body part 2 has an outletduct 8 opening through wall 18 and connecting with a chamber 10, intowhich a unit delivery connection can be attached. The wall 18 abuts astep 17 in the wall of the body part I. The parts 1 and 2 have a pushfit but alternatively they may also be connected by cooperating threadsections.

As stated previously the duct 9 widens to form a housing chamber andwithin this chamber is positioned the first piston member 3, which has acylindrical body part coaxially positioned relative to the part 1. Thismember 3 has a central passage 11 passing through it, which is influidconnection with the outlet duct 8 in the part 2. A flange 4 extendsoutwardly from the cylindrical part of the member 3 intermediate theends thereof. One end 12 of the member 3 is normally spaced from thewall 18 and the member 3 is biased from the wall 18 by a resilientannulus 5 positioned between the end wall 18 and the flange 4. Theperiphery of the flange 4 is spaced from the sidewall of the pumpchamber so that the member 3 may move in a reciprocal path to and fromthe wall 18. A space 7 is formed in the said chamber between the side ofthe flange 4 not contacted by the annulus 5 and a step face 16 of thebody part 1, and this space extends from the seal provided by theannulus 5 and constricted passage between a ball 6 and wall 13.

This ball 6, which is adapted to form a fluid seal with one end of thepassage 11 in member 3, forms the second piston member. The ball 6 alsoseats on a step seat 15 of the body part 1 and its diameter is such thatit is spaced from the sidewall 13 of the housing chamber by a smallamount to form a constricted fluid passage between the space 7 and theinlet duct9. v

This unit displaces fluid from the inlet duct 9 to the outlet duct 8 andthe operation of the unit will now be described, commencing with thecomponents thereof in the positions shown in the drawing As the fluidpressure in the inlet 9 increases the ball 6 and piston member 3 will bemoved against the resilient force of the annulus 5 and will displace thefluid through the outlet 8 until the end 12 of the member 3 contacts thewall 18. The annulus 5 and the seat between the ball 6 and member 3 areboth substantially fluidtight so that a piston action is obtained. Anyfurther increase in the fluid pressure .in the inlet 9 will not lead toany further displacement of the components and, therefore, the unit isnot responsive to an excessive pressure signal.

As the fluid pressure at the inlet 9 begins to fall while the pistonmembers 3 and 6 are still in their upper, displaced positions and therewill be a higher fluid pressure in the space 7, due to the resilience ofthe annulus 5 and because the space between the ball 6 and the sidewall13 is restricted This pressure in the space 7, acting downwardly on theouter diametrical part of the ball 6, will move it away from the member3 and towards its seat end of the inlet 9, which it will close, thuspreventing backflow of the fluid back to the inlet 9 through theconstricted passage between the ball 6 and wall 13. Instead, fluid fromthe space 7 will be discharged into the passage 11, thus allowing thepiston 3 to return to its lower position (as shown) ready for the nextpump stroke.

Any back pressure in the outlet 8 will assist in separating the ball 6from the piston member 3 but it will not otherwise affect operation ofthe device.

The other'embodiment of the invention is shown in FIG. 2 and includesfirst, second and third body parts 20, 21, 2 2 which are push-fittedinto each other. Alternately these body parts can be in screw threadedengagement. The first part'20 contains a housing chamber in which arepositioned the moving elements of the unit. This chamber increases indiameter in stepped increments from the inlet port 3.

A ball 23, which forms the second piston member, seats in fluid-sealingcontact on a step 24 in the housing chamber. A first piston member 25 isof generally cylindrical form, with an extension 26 of cylindrical formbut of smaller diameter. Within this extension is a passage 27 which isclosed at its inlet end by the ball 23, which contacts and seals withthe end of the extension 26. A space 28 is formed between the pistonmember 25 and the constricted passage which is present between the ball23 and the wall of the housing chamber within which the ball moves.

The first piston member 25 is in sliding contact with the housingchamber so as to seal the space 28 from the outlet 30. When the end ofthe passage 27 is closed by the ball 23. The first piston member 25 isbiased from the third body part 22 by a helical spring 29. This helicalspring extends within the cylindrical part of the first piston member25. Fluid under pressure enters its unit through the inlet port 31.

This embodiment operates in the same manner as described for the firstembodiment, and it being noted that the resilient annulus has beenreplaced by the spring 29 in so far as its biasing functions areconcerned. The sealing functions of the annulus 5 have been replaced bythe fluid seal between the sealing surfaces of the first piston member25 and the housing chamber. It will be noted that the movement of thefirst piston member 25 towards the outlet port is limited by theabutment of the piston 25 with the body part 22.

The modification by which the functions of the annulus 5 are achieved byother means to allow a longer stroke to be obtained by the piston member25. Thus, while the first embodiment has its stroke limited by thedimensions of the annulus 5, a comparatively larger stroke is possiblefor the second embodiment, due to the use of a helical spring. Thesecond embodiment is shown as including a filter element 32, thiselement removes contaminants which, for example, could interfere withthe flow of fluid through the constricted passage.

The embodiment of FIG. I may also have a filter element in the inletflow.

It will be noted that each embodiment has internally or externallythreaded sections at its extreme ends. Suitably adapted fluid-supplypressure duration and frequency of the signals represented byinterruptions in the supply pressure provided the signals reach acertain level of maximum pressure.

Although the present invention has been described by reference to onlytwo embodiments thereof, it will be apparent that numerous othermodifications and embodiments will be devised by those skilled in theart which will fall within'the true spirit and scope of the presentinvention.

What is claimed as new and desired to be secured by Letters Patent ofthe United States is:

1. A fluid displacement unit for delivering predetermined quantities ofa fluid supplied to it under pressure in response to periodic increasesand decreases in the said pressure, said unit comprising:

a housing chamber having an inlet and an outlet for said a first pistonwhich is reciprocable in said chamber and has a fluid passage extendingthrough it,

a second piston which is movable in said chamber between said inlet andsaid first piston which it engages to close said passage, said pistonstogether dividing a reserve space in part of said chamber from saidinlet and said outlet except for a constricted passage for allowingfluid under pressure to flow from said inlet and said space past saidsecond piston, and

resilient means biasing said first piston against said second piston toclose said passage whereby a supply of fluid to said inlet underpressure acts on and moves both said pistons together away from saidinlet and against the force of said resilient means to discharge fluidfrom said chamber to said outlet while fluid from said inlet enters saidreserve space through said constricted passage, whereas a drop inpressure in said inlet allows said resilient means to return said firstpiston to its original position, the pressure of the fluid in saidreserve space first moving said second piston away from said firstpiston to allow this fluid from said space to be discharged through saidpassage.

2. A fluid displacement unit according to claim 1, wherein said secondpiston after being moved away from said first piston closes said inletto prevent return flow of fluid through said constricted passage.

3. A fluid displacement unit according to claim I, wherein said secondpiston is a ball.

4. A fluid displacement unit according to claim 1, wherein saidconstricted passage is formed between said second piston and a wall ofsaid chamber.

5. A fluid displacement unit according to claim 1, wherein the saidbiasing means comprises an annulus made of a resilient material which iscompressed as said first piston is moved towards said outlet.

6. A fluid displacement unit according to claim 5, wherein said chamberhas a part of large diameter at its outlet end and a part of smallerdiameter at its inlet end and wherein said first piston has a radiallyprojecting flange intermediate its ends, said flange and said annulusbeing in engagement with each other and operating in said largerdiameter part of said chamber, and wherein the end of said first pistonaway from said annulus extends into said smaller diameter part of saidchamber, in which it is adapted to form a seal with said second piston.

7. A fluid displacement unit according to claim 1, wherein said annuluswhile it is compressed forms a fluid seal between said outlet and saidspace.

8. A fluid displacement unit according to claim 1, wherein the saidbiasing means is a helical spring.

9. A fluid displacement unit according to claim 8, wherein said firstpiston is slideable in and forms a fluid seal with the wall of saidchamber.

10. A fluid displacement unit according to claim 1, which comprises afirst body part in which said chamber and inlet are formed, and a secondbody part in which said outlet is formed,

said inlet and outlet being coaxial with each other and said resilientmeans being compressed in an axial direction between said first pistonand said second body part.

11. A fluid displacement unit for delivering predetermined quantities ofa lubricant supplied to it under pressure in response to periodicincreases and decreases in the said pressure, comprising:

a housing chamber having an inlet and an outlet for said lubricant;

first and second pistons movable in said chamber, said first pistonhaving a passage through it which communicates with said outlet andwhich is adapted to be closed by said second piston while the latter isheld against said first piston by the pressure of lubricant supplied tosaid inlet; and

biasing means acting on said first piston to force it towards the inlet;

the said housing chamber and pistons being so formed than together theyprovide a reserve space behind said first piston and a restrictedpassage connecting this reserve space with the inlet side of said secondpiston whereby a supply of lubricant under pressure to said inlet actson both said pistons and while holding said second piston against saidfirst piston to close said passage forces said pistons together towardssaid outlet to discharge a measured quantity of lubricant withoutsubstantial back leakage past said pistons and at the same time allowslubricant to enter said reserve space, and whereby a reduction in theinlet pressure causes the pressure of lubricant in said reserve space tomove said second piston away from said first piston to open the saidpassage through said first piston before said first piston completes itsreturn stroke.

'12. A fluid displacement unit accordingrto claim 11 wherein said secondpiston is in the form of a ball which closes the saidpassage in firstpiston during the delivery stroke of said pistons and closes said inletduring the return stroke of a said first piston,v said. restrictedpassage being provided by a -.clearance betur'eensaid ball and the wallof the said chamber.

1. A fluid displacement unit for delivering predetermined quantities ofa fluid supplied to it under pressure in response to periodic increasesand decreases in the said pressure, said unit comprising: a housingchamber having an inlet and an outlet for said fluid, a first pistonwhich is reciprocable in said chamber and has a fluid passage extendingthrough it, a second piston which is movable in said chamber betweensaid inlet and said first piston which it engages to close said passage,said pistons together dividing a reserve space in part of said chamberfrom said inlet and said outlet except for a constricted passage forallowing fluid under pressure to flow from said inlet and said spacepast said second piston, and resilient means biasing said first pistonagainst said second piston to close said passage whereby a supply offluid to said inlet under pressure acts on and moves both said pistonstogether away from said inlet and against the force of said resilientmeans to discharge fluid from said chamber to said outlet while fluidfrom said inlet enters said reserve space through said constrictedpassage, whereas a drop in pressure in said inlet allows said resilientmeans to return said first piston to its original position, the pressureof the fluid in said reserve space first moving said second piston awayfrom said first piston to allow this fluid from said space to bedischarged through said passage.
 2. A fluid displacement unit accordingto claim 1, wherein said second piston after being moved away from saidfirst piston closes said inlet to prevent return flow of fluid throughsaid constricted passage.
 3. A fluid displacement unit according toclaim 1, wherein said second piston is a ball.
 4. A fluid displacementunit according to claim 1, wherein said constricted passage is formedbetween said second piston and a wall of said chamber.
 5. A fluiddisplacement unit according to claim 1, wherein the said biasing meanscomprises an annulus made of a resilient material which is compressed assaid first piston is moved towards said outlet.
 6. A fluid displacementunit according to claim 5, wherein said chamber has a part of largediameter at its outlet end and a part of smaller diameter at its inletend and wherein said first piston has a radially projecting flangeintermediate its ends, said flange and said annulus being in engagementwith each other and operating in said larger diameter part of saidchamber, and wherein the end of said first piston away from said annulusextends into said smaller diameter part of said chamber, in which it isadapted to form a seal with said second piston.
 7. A fluid displacementunit according to claim 1, wherein said annulus while it is compressedforms a fluid seal between said outlet and said space.
 8. A fluiddisplacement unit according to claim 1, wherein the said biasing meansis a helical spring.
 9. A fluid displacement unit according to claim 8,wherein said first piston is slideable in and forms a fluid seal withthe wall of said chamber.
 10. A fluid displacement unit according toclaim 1, which comprises a first body part in which said chamber andinlet are formed, and a second body part in which said outlet is formed,said inlet and outlet being coaxial with each other and said resilientmeans being compressed in an axial direction between said first pistonand said second body part.
 11. A fluid displacement unit for deliveringpredetermined quantities of a lubricant supplied to it under pressure inresponse to periodic increases and decreases in the said pressure,comprising: a housing chamber having an inlet and an outlet for saidlubricant; first and second pistons movable in said chamber, said firstpiston having a passage through it which communicates with said outletand which is adapted to be closed by said second piston while the latteris held against said first piston by the pressure of lubricant suppliedto said inlet; and biasing means acting on said first piston to force ittowards the inlet; the said housing chamber and pistons being so formedthan together they provide a reserve space behind said first piston anda restricted passage connecting this reserve space with the inlet sideof said second piston whereby a supply of lubricant under pressure tosaid inlet acts on both said pistons and while holding said secondpiston against said first piston to close said passage forces saidpistons together towards said outlet to discharge a measured quantity oflubricant without substantial back leakage past said pistons and at thesame time allows lubricant to enter said reserve space, and whereby areduction in the inlet pressure causes the pressure of lubricant in saidreserve space to move said second piston away from said first piston toopen the said passage through said first piston before said first pistoncompletes its return stroke.
 12. A fluid displacement unit according toclaim 11, wherein said second piston is in the form of a ball whichcloses the said passage in said first piston during the delivery strokeof said pistons and closes said inlet during the return stroke of saidfirst piston, said restricted passage being provided by a clearancebetween said ball and the wall of the said chamber.
 13. A fluiddisplacement unit according to claim 11, wherein said biasing means isprovided by a ring of a resilient material which is compressed and formsa seal between said first piston and the outlet end of said chamber.